Process for the preparation of sulfonamides of the pyrimidine type



, wherein R and R have the same meaning as in'Formula preparation of sulfonamides of the formula i 3,132,139 r PROCESS non THE PREPARATION or SULFQNA- ,MIDES or run P Y i 1' TYPE Hermann Bretschneider, Innsbrk-Arzl, and Wilhelm Kliitzer and Joachim Schantl, Innsbruck, Austria, assignors to li-iotfmann-La Roche Inc, Nutley, l\l.J., a

corporation of New Jersey N Drawing. Filed June 8, 1962, sr. No. 200,925

Claims priority, application Switzerland June, 16, 1961 2 Claims. (Cl.260--239.75)

' The present invention relates to a novel process for the whe reinR and'R are lower alkyl groups, preferably those with 1- to 6 carbon atoms, e.g. methyl, ethyl, propyl, isopropyl, butyl, hexyl, etc.; and R can also be a hydrogen atom or an ---OR group.

The present process is carried out by removing the -SR group by hydrogenationfrom a compound having the formula 1 c g v R (fR 7 SR ;(II)

When X isan amino group precursor, the reaction prod- 3,132,139 Patented May 5, 196 1 group precursor inthe para-position, i.e. the amino group precursors defined above for compounds of Formula II.

Starting materials with a free amino group in the pposition can be prepared from the coupled products according to known methods for converting an amino group precursor into an amino group. For example, Z-methylthio-4-amino-o-methoxy-pyrimidine can be reacted with p-acetarnidobenzenesulfonyl chloride in pyridine at about 7 room temperature to form 2-methy1thio-4-(N -acetylsul- N -acetyl group on this compound can be a 2.5 g. of anhydrous sodium ,ture allowed to stand for one. hourinthe c'old. (Upon, acid, the filtrate yields not is converted into an amino group by known methods, forexarnple, hydrolysis or reduction. vThe. reduction of reducible; groups, such as the nitro group, can also, be

carried. outisimultaneously 'with thefhydrogenolysis of thefSR group; F or splitting oil of.N -acyl groups that may bepresent, such as the N -acetylgroup, the desulfurized reactionproduct obtained after the hydrogenolysis step'tneed "not be isolated. It can be. submitteddirect to rises to 205. 206 C.

saponilication, eg. by means oisodium hydroxide solu- 1 din a of FormulaII is heated inan'aiqueous s'odiumcarbori- 1ri ucing.carbon dioxidelgto pre v v 1, Thecoinpounds of Formulallwhich areused as start? ,1

ate or'arninonia solution in the presence of Raney nickel impregnated with hydrogen at the boiling point of the a a .According.to apr eferredprocess, an alkylthio pyrimi solution. The -SR group is'thereby split off. An N.;-

acylated product is convertedi'nto a compound of Formula I containing a 'free amino group by saponification, j;e ,'g-.;by. the addition of an alkali hydroxide, e g. sodium h'droxide to thereaction solution The compound of 1 frnula l can easily'be. recoveredfrom.thealkaline solu than the solation ireaches a of about 5;; .or by intro are the product.

g m 'fa'terials iin th e pr'ocess o f the. invention can be iprg. is Pin mi Q inidi -the tst i l ,drogry-pyrimidinev through". irrethylation of the 'hydroXy "groupbymeans of phenyltrirnethylamrnonium chloride, or

I from 2,6-dichloro-4amino-pyrimidine.by first converting i itginto'2-methylthio-4-amino-6 chloro-pyrimidine followed 1111. of hot water; J acetyl'sulfanilamido) fanilamido)-6-methoxy-pyrimidine in good yield. The readily split off, e.g. With methanolic' HCl, whereupon the Z-methylthio-4-sulfanilamido-6-methoxy-pyrimidine is obtained.

The compounds of Formula I prepared accordingto the process of the invention exhibit high antibacterialactivity, e.g. against staphylococcal, pneumococcal, or

Example 1 8 g. of 2-methylthio-4-(N -acetylsulfanilamido)-6- methoxy-pyrimidine were added to 150 m1. of water in carbonate. Then about 20 to about. 25 g. of Raney nickel [prepared according to Organic Synthesis 21, 15 (1941)] is added thereto: and the-mixture heated at the boiling point for three hours. .The mixture is cooled, 7 g. of sodium hydroxideadded, and the reaction product saponified by keeping the reaction mixture on a boiling water bath for 11.0.minutes. It is'then filtered hot, and the Raney nickel washed with two portions of 10' ml. each .ofhot water." The filtrate is'made" alkaline with sodium carbonate, and the mix neutralization with glacial acetic 5.6 g. of 4-sulfanilamido-6-methoXy-pyrimidine ofimelt ing point 190-202 (92% of theory). After several recrystallizations fromg50% ethanol, the melting 'point The 2 methylthio-4-(N -acetylsulfanilamido)-6-methorgypyrimidine used as the starting material can be"pre" p red as lo r 2.4 g. of Z-methylthio-4-amino-6-methoxy-pyrimidine are dissolved in 15 ml. of pyridine and 3.5 g. of pacetyl: amidobenzenesulfonyl chloride added at '20 C. The mixture; becomes colored red-brown in a slightly exothermic'reaction. After 24 hours at 20 Cn-the pyridine is evaporated ofi' at amaximum temperatureof C.

and the/residue triturated with,50 mLof waten The crystalsso obtained are dissolved in 100 ml. of 90% ethanol, the solution filtered and the filtrate added to 200 6 methoiry-pyrimidine of melting y the addition-0112111 ac'dQ for example; acetic acid, i

it reaction 'of The 2-rnethylthio}4-ainino :6 methoXy-pyrimidinej turn can be prepared from 2-m'ethylthio-4-amino 6-hyby 'methanolysis of the 6-chlorine atom.

, The. 2:methylthio 4 sulfanilamido :6 rnethq y py ri il dine used *as thestarting material for the desul furization the inventionEcan ,be prepared .fromits N I F absolute methanol and 0.4 g. bfI-ICI in 1.5 nilf'of absol'utej methanol added thereto." The mixture is heated After cooling, Z-methylthid t-(Nf '7 or. under reflux for one hour with exclusion of moisture. The solvent is removed under vacuum, and the residue digested with 12 ml. of 2 N hydrochloric acid, whereupon almost all of the solids go into solution; -After standing for one hour at the solution is filtered, made alkaline with sodium carbonate, and filtered again after standing for thirty minutes at 0 C. The filtrate is neutralized with CO until the mother liquor is clear. 1.3 g. of 2-methylthio-4-sulfanilamido 6 methoxy-pyrimidine of melting point 170-175 C. (76% of theory) is obtained thereby. After recrystallization from 50% alcohol, the meltingpoint is 176-178 C.

Example 2 g. of 2-methylthio-4-(N -acetylsulfanilamido )-5- ethyl G-methOXyyrimidine is heated with 80 ml. of water,

Example 4 2 g. of 2-methylthio-4-(N -acetyl-sulfanilamido)-5- rnethyl 6-methoxy-pyrimidine are dissolved, while heating gently, in a'soluti-on of 1.5 g. of sodium carbonate and 70 ml. of Walter. 5-6 g. of Raney tnickel are added 5"ml.'of concentrated ammonia, g. of Raney nickel and the mixture heated to 8590 for one hour on a I steam bath. The mixture is treated with charcoal, filtered, andthe. alkaline filtrate acidified to pH 5 with acetic acid. Practically pure crystalline 4-sulfanilamido- S-ethyl-6-methoxy-pyrimidine is obtained thereby; melting point l86-l87 C. (from acetonitrile).

.' The 2-methylthio-4-(Nyacetylsulfanilamido)-5-ethyl-6- methoxy-pyrimidine used as the starting material can be obtained as follows:

56 'g. of-p-acetoamidobenzenesulfonyl chloride is added to ,44' g. of Z-methylthio-4 amino-5-ethyl-6-methoxy-pyrimidinein 240 ml. of absolute pyridine at 25 C., and the mixturev stirred for 24 hours at this temperature. After the addition of 100 ml. of Water, the pyridine is almost completely removed by distillation under vacuum, the residue triturated with 350 ml. of water, and the crystals filtered off. 68 g. of 2-methylthio-4-.(N -acetylsulfa- -nilamido)-5-ethyl-6-methoxy-pyrimidine of melting point 256-260" is obtained thereby. After recrystallization from acetonitrile, the melting point is 259-260 C.

2-niethylthi0-4-amino-5-ethyl 6 methoxy-pyrimidine can in turn be preparedas follows:

Ethylcyanoacetic acid ethyl ester isjcondensed with thiourea to form 2-thio-4-amino-5-ethyl-6-hydroxy-pyrimidine (melting point 299-301 C. from ethanol), which is methylated on the mercapto group with dimethyl sulfate, and the Z-methylthio-4-amino-5-ethyl-6-hydroxypyrimidine (melting point 221-222 C. from dioxane) jobtained thereby is converted to 2-methylthio-4-amino-5- ethyl-6-methoxy-pyrimidine (melting point 102-104 C. from'butyl oxide) by means of"phenyltrimethyl'a'mmonium chloride. I Example 3 8.6g. of 2-methylthio-4-sulf anilamido-5-ethyl-6-methoxy-pyrimidine are suspended in 80 ml. of water, and 5 thereto and the solution; is refluxed for 2% hours and filrte-red hot. By acidifying the filtrate with dilute hydrochloric acid, there are obtained 1.2 'g. (65%) of 4-(N acetyl sulfanilamido) -5 methyl-6-methoxy-pyrimidine of melting point 228-231 (from water/ethanol).

The product thus obtained is saponified on a water bath for 1 /2 hours with 12 ml. of 1 N sodium hydroxide soluti-on. 'Aliter coolingand filtration, the filtrate is acidified (Congo red) with dilute hydrochloric acid. The undissolved residue is filtered off. The filtrate is cautiously rendered alkaline by means of concentrated ammonia, whereupon the pH of thesolution is brought to 5-7 with glacial acetic acid. .085 g. (81%) #of 4-sulfanilamido-5- methyl-6-methoxy-pyrimidine of melting point 214-217 (from water/ethanol) is obtained thereby.

The 2-methylthio-4- (N acetybsulfanilamido) -5methyl- 6-methoxypyrimidine used as starting'material can be obtained as follows: V i

1.5 g. of 2-methylthio-4-amino-5-methyl-6-methoxypyrimidine and 2.4 g. of p-acetarnidobenzenesulfonyl chloride are dissolved in 10 ml. of absolute pyridine and allowed to stand for '24 hours at room temperature. Then, 100 ml. of water are added and the reaction product brought to crystallization. There are thus obtained 2.5 g. (80%) pt 2-methylthio-4-(N acetyl-sulfanilamido)-5- methyl-6-methoxy-py-rimidine melting at 265-268" (from water/ethanol). g I t 2 methylthio-4 armino-5-methyl-6-methoxy-pyrimidine can in be prepared as follows:

ml. of concentrated ammonia and 20 got Raney nickel Lprepared according to Organic Synthesis 21, 15 (1941)]- are added thereto. The reaction mixture is heated with stirring for 4 hour; 2 m1l of xylene being added to prevent foaming. The reaction mixture is then filtered hot,

the Raney nickel washed with hot'water made alkaline with ammonia; and the filtrate acidified with aceti'cfa'cid to pH 5. s or 4-.sulfanilamido-5{ethyl-6-methoxypyrimidine of melting point 186-187" (from acetonitrile) is obtained thereby. The 2; methylthio-4-sulfanilamido-5-ethyl-6-methoxypyrimidine used as starting "materiallcan be" obtained as follows from its N -acetyl derivative: i I 24 g. of 2-methylthio 4 .(N -acetylsulfanilamido)-5 ethyl-6;methoxypyrimidine.= are heated Iwith--350 ml. of:

--methanolic HCl (2.6%) for two-hours undenre'flux. prep-aredas follows:

After eyaporation: under vacuum, the residue is, stirred into a paste with 'water, and? N sodium hydroxide solufor 3 /2 hours in thepresence of 6-7 g. of Raney nickel.

Then, a solution of 1g. of rsoldlum liydroxide in 3 of t water isadded thereto andheating continued for another (a) u-cyano propionic acid ethyl ester is condensed with thiourea, in the presence of sodium ethylate, to form 2athio-4 amino 5-methyl-6-hydroxy-pyrimidine;

(b) The sodium salt of the above product is methylated with dimethyl sulfate to form 2-methylthio-4-amiuo-5- methyl-6-hydroxypy-rimidine of M.P. 230. (from water/ ethanol); and

' (0) The sodium salt ;of the product thus obtained is methylated with phenyl trimethylammonium chloride in the presence of dimethyl fonmamide. to form Z-methy-lthio 4 amino 5-methyl-6-methoxypyrimidine of M.P.

1 16-119 (from waiter).

1 I Examples 1.3 g. of 2 methylthio-4-(N -acetyl-sulfauilamido)-5,6-

dimethoxy-pyrimidine (arev dissolved in 25 ml. of water and 0.4 g. of anhydrous sodium carbonate, then refluxed hour. The catalyst is filtered oif and the filtrate acidified to Con-gored withfhydrochloric ac-id. f The pH is then broughit'to 5 by means of ammonia, thus causing crystallization. There is thus' ohtained 0.51 g. of 4-sulfanil amido-Sfi-diniethoxY-pMdineof M.P. 190-194 (from 50% ethanol).' Y

The Z-methylthio 4 N acetyl-sulfanil=amido)-5,6- dirriethoxy-pyrimidine used as starting material can be 0.9 g. 0fZ IIIQthYltlIiOJ aQliIlO-5,6-dlm6th0XY-py1lmi dine-are dissolved infi ml. of gabsol ute pyridine. At 0 t 1.2 g. of p-acetylamidobenzenesuifonyl chloride are added thereto and the mixture is shaken until all the materialis dissoi-ved. The solution is allowed to stand for 22 hours at and the pyridine eliminated in vacuo at 20. '110 the resulting product are added 20 m1. of Water and 3 mi. of glacial acetic acid, whereupon the whole mixture is heated to theboil, thus causing crystailization. The crude prodnot obtained is dissolved in 40 mi. of 2.5% soda solution, and the solution obtained is filtered and 'oversatluate d with gaseous carbon dioxide. There is thus obtained 1.5 g. (85% of 2-methylth1'o-4-(N -acetyl-sulfianiiarnido -5,6-

' dimethoKy-py rimidine of M.P. 220221 (from 50% ethanol) 2-methyllthio-4-amino-5,6-dimethyl-pyrimidine can in turn be prepared as iollowsz' (a) n-Methoxy-cyanoacetic acid methyl ester is condensed with thiou-rea, the presence of sodium methylate, to form 2-thio-4amino5-methoxy-6-hydroxy-pyrimidine,

(b) The product thus obtained is methylated in a sodium methylate solution with methyl iodide to form 2 methyithio-4-amino-5anethoxy-6-hydnoxy-pyrimidine of M.P. 203 (from water), and

I (c) The latter product is methylated with phenyl-trimethyllammoiuu-rnioluenesulfionate to form 24methyi 'thio-4-amino-5,6-dimethoxy-pywimidine of M.P. 112 1 15 (from 20% methanol).

We claim: 1 1. A process for the preparation of a sulfanilamide of the formula wherein R is lower alkyl comprising the step of hydrogenating a compound of the formuia R0 OR References Cited in the file of this patent UNITED STATES PATENTS 2,430,439 Winnek et a1 u Nov. 4, 1947 FOREIGN PATENTS 866,843 7 Great Britain May 3, 1961 OTHER REFERENCES Beamanz' J. Am. Chem. Soc, vol. 76, pp. 5633-5636, 1954.

Khauasch: Organic Sulfur Compounds, vol. 1, pp. 519- Budesinsky et :aL: 130, 1961.

Bretschneider et Manatsh Chem, vol. 92, No. 1, pp.

Experimentia, vol. 17, N0. 3, 129 

1. A PROCESS FOR THE PREPARATION OF A SULFANILAMIDE OF THE FORMULA 